Process for fluorinating hydrocarbons



Patented Sept. 5, 950

PROCESS FOR FLUORINATING nrnaocarmons Anthony F.-Benning, Woodston, N. 1., assignor to the United States of America as represented by the United States Atomic Energy Commission No Drawing.

. 2 Claims. 1 This invention relates to the manufacture of high boiling fluorination products and is particularly directed to a new method for treating highboiling hydrocarbons to convertthem to fluorocarbons. v

In the past it has been proposed to fluorinate hydrocarbons by passing vapors of the hydrocarbons into contact with metal fluorides such as silver difluoride, cobalt trifluoride and manganese trifluoride at temperatures between 150 and The process, has been found to be capable of producing high yields of .fluorocarbons from hydrocarbons of low molecular carbon content such as heptane; Application of the process to high boiling hydrocarbons such as lubricating oils has given disappointing results from the standpoint. of yields of fluorocarbons; thus, yields of about to of the theoretical yield represent the maximum yields that have been obtained. The balance of the hydrocarbon is broken down into compounds containing fewer carbon atoms in the molecule so that the product comprises nearly twice as much scission and fluorinolysis products as simple fluorination products.

Attempts to effect the fluorination of high-boiling hydrocarbons in liquid phase, when conducted at low temperatures, have resulted in the formation of polymerization products, and when conducted at high temperatures, have resulted in violent and explosive fluorinolysis of the hydrocarbons.

It is an object of the present invention to provide a process for the fluorination of high-boiling hydrocarbons to produce substantially higher yields of simple fluorination derivatives than obtainable by processes hitherto employed. A further object is to provide a liquid phase process which proceeds rapidly and smoothly and which is easily controlled. Further objects will appear from the following description of the invention.

In accordance with the present invention a high-boiling hydrocarbon is reacted in liquid phase with a fluorinating agent of the group consisting of silver difluoride, cobalt trifluoride and manganese trifluoridein a reaction medium comprising a high-boiling fluorocarbon solvent at a reactionftemperature between 150 C. and 400 C.

By the process of the invention yields of simple fluorination products amounting to 60% to 75% of the theoretical yields have been obtained.

The process is particularly applicable to petroleum derivative fractionsboilinz above 300 C. at normal atmospheric pressure (760 mm.); pe-

Application November 30, 1944 Serial No. 565,987

. 2 troleum lubricating oil fractions distilling at temperatures between 200 C. and 300 C. at'10 mm. of mercury absolute pressure are illustrative of this type of material.

Fluorocarbon solvents suitable for carrying out the process are highly fluorinated carbon compounds which boil above about 180 C. and which are fluid liquids at temperatures in the vicinity of their boiling points. Liquid fluorocarbon frac tions boiling from 210 C. to 220 C. or from 180 C. to 250 C. have been employed with satisfactory results. Mixtures containing small proportions of materials boiling below 180 C. may be used but it is desirable that the average boiling point of the bulk of the solvent be about 220 C. or higher to avoid application of elevated pressures to prevent excessive vaporization during the fluorination,

The fluorocarbon solvent may contain a small proportion of elements other than fluorine and carbon. For instance, compounds containing an atom of residual hydrogen in the molecule may be used. Although part of this hydrogen may be replaced by fluorine during the process, the reaction produces an equally desirable solvent and is not sufliciently energetic to alter the character of the main reaction or to interfere seriously with its control. Likewise small proportions of other elements such as chlorine, bromine, oxygen or nitrogen may be present in the molecule without materially affecting the predominantly fluorocarbon character of the solvent.

Some fluorinolysis occurs in the process of the invention and produces by-products having a boiling range below that of the principal fluorination products. These by-products may be used satis:

to the next fluorination for use as fluorocarbon v solvent therein.

It is preferred to conduct the process at temperatures rising gradually from an initial temperature between C. and 200 C. to a final temperature between 250 C. and 300 C. However, since the fluorocarbon products are highly stable materials, the flnal temperature may rise substantially above the preferred temperatures without material reductionin yield of fluorocarbon products. The ratios of fluorocarbon solbon. a substantially higher ratio is desirable. In

both cases good agitation promotes uniform reaction and reduces the minimum quantity of solvent required.

The process may be conducted at atmospheric or at elevated pressures. In view of the fact that highpressuresareunnecessary,pressuresinthe neighborhood of atmospheric pressures and hence not requiring special pressure equipment are preferred.

Theprocessmaybecarriedoutinanapparatus of any convenient material of construction. However, the fluorination agents employed attack iron equipment and consequently equipment of nickel or Monel metal is preferred.

The following examples, in which quantities are expressed as parts by weight, will further illustrate the process of the invention.

Example 1 parts of a lubricating oil of petroleum origin and having the following distillation characteristics at 10 mm. of mercury absolute pressure:

(a) Initial boiling point, 183 C., (b) 2% over at 226 C.,

(c) over at 242' C..

(d) 95% over at 253 C.,

is mixed with 500 parts of a fluorinafed kerosene fraction having a boiling range of 210 C. to 222" C. at 760 mm. The mixture is agitated and 1150 parts of silver difluoride are added gradually in a period of about 4 hours, during which the temperature is raised gradually to 210 C. The mixture is maintained at this temperature for an additional 10 hours.

It is then allowed to cool to room temperature and about 1500 parts of trifluorotrichlorethane" is added to reduce the viscosity of the mixture. The silver difluoride residue is filtered oil, and the flltrate is distilled up to a temperature of 140 C. at 10 mm. of mercury absolute pressure to remove the solvents.

The residue is fractionally distilled yielding the following fluorocarbon fractions:

(a) 8 parts or distillate from 140 C. to 160 C. at 10 mm. and having a refractive index (sodium-D-line) of 1.330.

(b) 52 parts of distillate from 160' C. at 10 mm. to 185 C. at 0.4 mm. and having a refractive index (sodium-D-line) of 1.345.

(c) 37 parts of distillation residue.

The parts of fluorocarbon distillate corresponds to a yield of about of theoretical.

Example 2 The following fluorocarbon fractions are obtained:

(a) 11 parts of distillate from to C. at 10 mm. and having a refractive index (sodium- D-line) of 1.331.

(b) 55 parts of distillate from 160 C. at 10 mm. to 195 C. at 0.4 mm. and having a refractive index (sodium-D-line) of 1.343.

(c) 1.6 parts of distillation residue.

The 66 parts of fluorocarbon distillate corresponds to a yield of about 71% of theoretical.

Example 3 Into a closed nickel kettle provided with a nickel agitator, 500 parts of silver difluoride and 210 parts of a fluorocarbon solvent are charged. The fluorocarbon solvent is a fluorocarbon fraction having a distillation range of 200 to 250 C. at atmospheric pressure and obtained in part by the vapor phase fluorination of kerosene by cobalt trifluoride and in part as a by-product of a preceding fluorination of a lubricating oil fraction by silver difluoride.

The mixture of solvent and silver difluoride is heated to about C. and agitated continuously under reflux.

10.5 parts of a petroleum lubricating oil fraction (distillation characteristics at 10 mm. absolute pressure: 5% over at 200 C., 95% over at 283 C.) is then added gradually in about 3% hours while the temperature is maintained between C. and 190 C. When all of the oil has been added, the temperature is raised to 215 C. and the mixture is agitated for an additional 10 hours. It is then cooled to about 60 C. and 300 parts of trifluorotrichlorethane is added and mixed with the reaction product for 10 minutes.

The mixture is allowed to settled and liquid is decanted from the kettle and transferred to a still. An additional 300 parts of trifluorotrichlorethane is added to the kettle and mixed for 15 minutes. The liquid is again decanted oil from the kettle and added to the still.

The contents of the still are then heated to 180 C. to remove trifluorotrichlorethane and any other low-boiling material. The residue is distilled under a reflux column to a temperature of 140 C. at 10 mm. of mercury absolute pressure (equivalent to about 250 C. at 760 mm.) to remove fluorocarbon solvent; there remains as crude fluorocarbon product 28 parts of liquid distillation residue.

At least a part of the fluorocarbon solvent is returned to the reaction vessel for use as solvent for a subsequent charge. This solvent comprises by-products from the fluorination process as well as fluorocarbons derived from kerosene, as described in the flrst paragraph of this example.

The distillation residue is reflned by the following procedure.

The residual liquid is heated to a temperature of about 85 C. and for each 28 parts of liquid 28 parts of silver difluoride is added gradually while the mixture is agitated. After addition of the silver difluoride is completed, the mixture is further heated in a period of about 4 hours to 210 C. and held at this temperature for 15 minutes. It is then cooled to 100 C. and an additional 28 parts of silver difluoride is added.

The mixture is again heated, this time to 240 C. in a 4 hour period and maintained at this temperature for 10 hours. It is then cooled to between 25 C. and 30 C. and 35 parts of trifluorotrichlorethane is added to reduce the viacoslty of the liquid. Solid matter is allowed to settle and the liquid is decanted oil.

35 parts more of trifiuorotrichlorethane is added and the liquid is again decanted from the solid matter and passed to a still. The liquid in the still is then distilled at atmospheric pressure to remove the trifluorotrichlorethane solvent and is then distilled to a final temperature of 100 C. and a final pressure of mm. of mercury absolute to separate low-boiling fiuorinated hydrocarbons. 20 parts 01' refined fluorocarbon oil is obtainedas distillation residue.

This method of refining fluorocarbon products of the type produced by the process of the present application is the subject of my U. S. Patent application Serial Number 541,300, flied June 20, 1944, and entitled Refining of Fluorocarbons."

Example 4 To a well agitated mixture 01' 1000 parts of AgF'z (100%) and 93 parts oi solvent comprising a mixture of fluorocarbons and having a boiling range of 130 C. at 760 mm. to 137 C. at 10 mm. is added 18.5 parts of a petroleum hydrocarbon oii fraction, having a boiling range at 10 mm. of 169 to 257 C. over a period of 5 hours while the mixture is maintained at 180-200" C. The charge is heated under reflux for 10 hours at V 240 C. and then cooled to 45 C. The mixture is washed well with trifiuoro-trichloroethane (CClzFCClFz). This trifluoro-trichloroethane is removed from the washings by distillation at atmospheric pressure. Forty parts of product consisting .01 a mixture of highly fluorinated hydrocarbons having a boiling range at 10 mm. pressure of 137 to 230 C. is collected.

It will be understood that I intend to include variations and modifications of the invention and that the preceding examples are illustrations only and in no wise to be construed as limitations upon the invention, the scope of which is defined in the appended claims, wherein I claim:

1. The method of fluorinating a petroluem lubrlcating oil which boils at atmospheric pressure at temperatures above 300 C., by replacement of the hydrogen atoms thereof with fluorine atoms and with a minimum formation of scission, polymerization and fluorinolysis products, which comprises heating said lubricating oil for several hours at temperatures between 150 C. and 400 C. in liquid phase contact with a fluorinating agent of the group consisting of cobalt trifluoride, silver difluoride and manganese trifluoride in a liquid fluorinated petroleum fraction which boils above 180 C. at atmospheric pressure, adding trifluorotrichlorethane to the reaction mixture to reduce its viscosity, separating the used inorganic fluorinating agent from the organic reaction products and solvents, and then fractionally distilling the organic reaction products and solvents to remove trifluorotrichlorethane therefrom and to separate fluorocarbon solvents of medium boiling points from fluorocarbon oils of high boiling points.

2. The method of fluorinating a petroleum lubricating oil fraction boiling above 300 C. at normal atmospheric pressure by replacement of the hydrogen atoms thereof with fluorine atoms and with a minimum formation of scission, polymerization and fluorinolysis products which comprises heating said petroleum fraction in a. fluorocarbon solvent boilingabove 180 C. at normal atmospheric pressure with a fiuorinating agent of the group consisting of cobalt trifluoride, silver difluoride and manganese trifluoride at temperatures between 150 C. and the boiling temperature of said fluorocarbon solvent, cooling the reaction mixture, adding trifluorotrichloroethane to the cooled reaction mixture to reduce its viscosity and to dissolve the fluorinated lubricating oil and the fluorocarbon solvent, separating the solid used inorganic fluorinating agent from the solution of fiuorinated lubricating oil and fluorocarbon solvent in trifluorotrichlorethane, removing trifluorotrichlorethane from said solution by distillation, and then fractionally distilling the residual solution of fluorinated lubricating oil in fluorocarbon solvent to separate fluorocarbon solvents of medium boiling points from fluorocarbon oils of high boiling points.

ANTHONY F. BENNING.

REFERENCES CITED The following references are of record in the flieof this patent:

UNITED STATES PATENTS OTHER REFERENCES Run at al., Zeitschritt fur Anorg. a Allg. Chemie, vol. 219, pp. 143-8 (1934).

Rufl et al., Angewandte Chemie, vol. 47, page 480 (1934).

Jockusch, Naturwissenschaften, vol. 22, P ge 561 (1934).

"Chemical Abstracts, vol. 26, page 1258 (1932). Abstract in article by Bull et al.

Mellor, "Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. 12, page 344; vol.

14, pages 608-9.

Henne et al., J. A. C. 8., vol. 63, page 3478 (1941) But! 8: Keim, Z. fur Allg. Chem, vol. 201, pages 

1. THE METHOD OF FLUORINATING A PETROLUEM LUBRICATING OIL WHICH BOILS AT ATMOSPHERIC PRESSURE AT TEMPERATURES ABOVE 300*C., BY REPLACEMENT OF THE HYDROGEN ATOMS THEREOF WITH FLUORINE ATOMS AND WITH A MINIMUM FORMATION OF SCISSION, POLYMERIZATION AND FLUORINOLYSIS PRODUCTS, WHICH COMPRISES HEATING SAID LUBRICATING OIL FOR SEVERAL HOURS AT TEMPERATURES BETWEEN 150*C. AND 400* C. IN LIQUID PHASE CONTACT WITH A FLUORINATING AGENT OF THE GROUP CONSISTING OF COBALT TRIFLUORIDE, SILVER DIFLUORIDE AND MANGANESE TRIFLUORIDE IN A LIQUID FLUORINATED PETROLEUM FRACTION WHICH BOILS ABOVE 180*C. AT ATMOSPHERE PRESSURE, ADDING TRIFLUOROTRICHLORETHANE TO THE REACTION MIXTURE TO REDUCE ITS VISCOSITY, SEPARATING THE USED INORGANIC FLUORINATING AGENT FROM THE ORGANIC REACTION PRODUCTS AND SOLVENTS, AND THEN FRACTIONALLY DISTILLING THE ORGANIC REACTION PRODUCTS AND SOLVENTS TO REMOVE TRIFLUOROTRICHLORETHANE THEREFROM AND TO SEPARATE FLUOROCARBON SOLVENT OF MEDIUM BOILING POINTS FROM FLUOROCARBON OILS OF HIGH BOILING POINTS. 